Senior fellow and research director in public law at the Brookings Institution; author of "Confirmation Wars"

The impending retirement of Justice David Souter will inevitably spark talk of the "balance of the court" and President Obama's opportunity to "shore up" its liberal flank. Blessed with a crushing Senate majority, Obama can do just about anything he wants with this nomination. The temptation, and pressure, to think about it in ideological terms -- that is, to seek a nominee whom he can count on as predictable vote on hot-button issues -- will be enormous. But he should resist it.

The delusions of some activists aside, liberals are not about to storm the Supreme Court. The conservative justices are younger, for one thing, and liberalism in any event is rather conflicted about what it wants in justices -- the only major point of agreement these days being that it doesn't want conservatives. Whomever President Obama puts on the court is going to have to spend many years working with young, energetic, conservative justices in the prime of their own careers. This person is likely, but not certain, to be joined by other, relatively younger Obama appointees. But absent long-term Democratic control of the presidency, those justices could easily fail to attain a majority. For a new justice to be effective, in other words, he or she will have to be capable of a constructive engagement with conservatism -- someone with a common language for dialogue with a group of justices who are not going anywhere anytime soon.

This is not what Obama's base will demand of him. It is, however, what he should demand of a nominee. The alternative is a continued division of the court into philosophical camps with ever-greater power concentrated in the hands of Justice Anthony Kennedy's swing vote.

Deputy attorney general in the Clinton administration; partner at WilmerHale

The conservative justices have been driven in a cohesive way by an ideology. A similar approach from the left will not counter that. Instead, President Obama needs to rebuild from the center on the principled pragmatism of Justices Ruth Bader Ginsburg and Stephen Breyer. The key factors of his nominee must be intellect, broad experience and personality.

Moving the court back from its considerable rightward drift will require a justice who can persuade from the high ground. He or she must be well-regarded by fellow justices and the Bar for knowledge of the law and must be able to effectively advocate within the councils of the court.

Service on the bench is helpful, but the high court needs justices who, like Justice Ginsburg, have also lived and worked in the real world, who have actually counseled clients and argued cases, whether in government, in private practice or in the public interest. With so many almost-lifelong judges on the bench, we risk losing an appreciation for how the work of the court is expressed in the world. That is a perspective from which to persuade.

Finally, the court needs a force of cohesion, someone who can, as Justice Brennan did, bring fellow justices together with patience, humor and humanity.

There is already considerable speculation about who the president's nominee will be and whether it should be a woman. I would certainly welcome a woman's nomination, but I don't believe there should be reserved seats on a court. To me, the most important thing is that we have someone who can represent the people of this country without adhering to any particular ideology. The Supreme Court should not be arch-liberal or arch-conservative. The most critical qualifications for any nominee are a substantive knowledge of the U.S. Constitution and its application over time, along with an understanding of the real effect that Supreme Court decisions have on people's daily lives.

I urge President Obama to nominate a woman. A woman of color would go even further toward broadening the narrow makeup of the high court, which today does not reflect the proud diversity of the United States.

Simply put, one is not enough, even if she happens to be the estimable Justice Ruth Bader Ginsburg. When 51 percent of the country is female, one justice out of nine is a court out of balance.

Ginsburg has been candid of late. She misses Justice Sandra Day O'Connor's input and has said that having only one woman on the court sends the wrong message. She also noted that women bring a life experience to the court that men can't. Indeed, research shows that female judges are "more likely than their male counterparts to have experienced sex discrimination and conflict between their work and family roles" and that they "more firmly rejected traditional stereotypical descriptions of women." After two years of Roberts and Alito, that's change we can believe in.

President of the Ethics and Public Policy Center; former clerk to Justice Antonin Scalia

President Obama has promised -- or, rather, threatened -- to select Supreme Court justices who will indulge their own subjective passions, their "deepest values" and "the depth and breadth of [their] empathy" in deciding what the Constitution means. He's even said that the "critical ingredient" in judging the "truly difficult" cases "is supplied by what is in the judge's heart." That's a recipe for the same sort of lawless judicial activism that has poisoned American politics for decades, most notably with Roe v. Wade's removal of abortion policy from the ordinary processes of representative government.

Obama should abandon his threat and embrace a more venerable brand of liberal judging. When conservative justices in the early decades of the 20th century invoked "substantive due process" to strike down progressive economic and social legislation, liberals vigorously -- and, ultimately, successfully -- advocated principles of judicial restraint.

Judicial restraint respects the Constitution's separation of powers and recognizes that the Constitution creates a system of representative government that leaves most matters to democratic processes for decision making. Judicial invalidation of democratic enactments is warranted only when those enactments clearly violate the Constitution.

Today, the liberal version of judicial restraint would construe Congress's legislative powers broadly and be skeptical of the various constitutional challenges that will be levied against Obama's domestic agenda.

Alas, the once-dominant species of liberal proponents of judicial restraint has relatively few surviving members. Obama should find them -- why not José Cabranes, the excellent judge whom President Bill Clinton appointed to the 2nd Circuit? -- and help revive the species. Doing so would make great strides toward ending the judicial wars and restoring proper respect for Americans' democratic powers.

Head of the Office of Legal Counsel in the Clinton administration; partner at O'Melveny & Myers

During the campaign, candidate Obama said that he would seek justices with a capacity for "empathy." Some critics said that empathy was an illegitimate, lawless criterion. This afternoon, the president doubled down: "I will seek someone who understands justice isn't about some abstract legal theory or footnote in a case book. It is also about how our laws affect the daily realities of people's lives."

The president is right to reject the idea that judging is a mechanical exercise. It requires the exercise of judgment, which makes room for a candid consideration of how legal rules do affect the daily realities of people's lives.

Far too few judges, liberal and conservative, candidly acknowledge that the questions before them are difficult, the answer often not clear, the history not fully accessible and the text far from unambiguous. Majority and dissenting opinions are too often written with untenable certitude about the "clearly right answer." As my Duke Law School colleague Jefferson Powell wrote in his book "Constitutional Conscience," a truly ethical judge will be honest about the inescapable fact "that constitutional decision making is a creative endeavor" and will "make the arguments to herself and others with candor, including an overt recognition of the ambiguities and uncertainties [involved]." The good judge will employ her legal craft "not to conceal difficulties or hidden springs of decision but to render them transparent and thus to enable the reader to evaluate critically the conclusions reached by the writer." With that honesty about the inevitability of choice should come humility about one's role as a judge.

President Obama has said that he intends to nominate to the Supreme Court judges who have a "heart" and who understand the "real-world" experiences of Americans. Some conservatives have attacked this standard. For instance, Wendy Long, chief counsel to the Judicial Confirmation Network, wrote that if Obama chooses a nominee "who rules based on her own 'deepest values' and what's in her own 'heart' -- instead of what is in the Constitution and laws -- he will be the first American President who has made lawlessness an explicit standard for Supreme Court Justices." This argument draws a false dichotomy. It proceeds from the false assumption that in the realm of constitutional adjudication, there is a single "right" answer that can be arrived at simply through deductive reasoning. Most lawyers would laugh at such a notion, and it is no coincidence that conservative justices embracing a "strict constructionist" view tend to see the Constitution in ways favoring conservative political positions.

A justice can have both a keen mind and a big heart, as Justice Souter and Justice William Brennan have shown. Choosing such a justice is not an embrace of lawlessness but a moral imperative.

President of Alliance for Justice, a coalition of public interest organizations

President Obama has an opportunity to name the strongest possible voice for upholding the Constitution and ensuring equal justice and basic freedoms for everyone in America, not just a few. That's what is needed to stand up to the relentless assault on the Constitution by judges appointed in the past eight years, too many of whom make decisions based on their own political agenda, contributing to an America with one set of rules for those at the top and another for the rest of us.

To find the best nominee, Obama should draw from a rich pool that includes not only federal and state judges but also state attorneys general, law professors, public-interest legal experts and elected officials with practical legal experience.

Most Republican senators can be expected to oppose any worthy nominee, so nothing is to be gained by nominating someone who is not a strong and effective voice for core constitutional values. Many of those senators are on record explicitly opposing filibusters of judicial nominees; their hypocrisy should be exposed if they attempt to block a majority vote.

Even before Sen. Arlen Specter announced he was changing parties and Al Franken's Minnesota victory was clear, Republicans in Congress were losing strength as fewer voters identified with their agenda. They should not be allowed to stand in the way of a nominee who will uphold the Constitution.

Author of "Exporting American Dreams: Thurgood Marshall's African Journey"; professor of law, history and political science at the University of Southern California

President Obama should nominate someone whose life experience provides a perspective that the current justices lack. Diversity in court appointments is often thought of in terms of the nominee's race or gender. Obama should go beyond simple identity politics. He should choose someone like Justice Thurgood Marshall, who encountered segregation and discrimination and whose law practice was a critical part of the experience he brought to the court. Marshall represented African American defendants in Southern courtrooms and saw firsthand the way the criminal justice system could be stacked against people of color and the poor. He applied that understanding to his work on the bench.

The next justice must understand that legal principles are not simply abstractions but have immediate and long-term consequences in the lives of individuals and communities. Perhaps Obama's nominee will have represented clients in deportation hearings, served low-income families in a legal aid office, or advised gay and lesbian members of the armed services. At this moment in American history, a nominee who has represented detainees at Guantanamo could bring important insights into the court's deliberations and further signal a change in the nation's posture toward human rights.

And for his nominee to be effective on a conservative court, Obama should look for a coalition-builder -- someone able to find common ground not only with Justice Anthony Kennedy, whose vote is often dispositive, but also with more conservative justices.

Former deputy chief of staff to President Bill Clinton; founder of the government relations firm Nueva Vista Group

Hispanic groups across the country will fight for the first Hispanic justice. Women's groups will argue for at least one more female justice. Civil liberties, civil rights and social justice advocates are desperate to have a justice who believes the Constitution is a living document, as a counter to the focus by Antonin Scalia and John Roberts on "original intent." Antiabortion groups see this decision solely through that prism.

To that cacophonous fray, I would add another criterion: individuals who have had real life experience and known more than the ivory tower of the appeals courts, from which presidents have lately chosen their Supreme Court nominees. I want someone who has a broad mix of skills and experiences, with a stellar legal mind. Why not a governor or an attorney general, or someone who has been responsible for implementing legislation at the federal or state level? We need someone who understands that Supreme Court decisions have real consequences and affect people's daily lives. I hope President Obama is thinking about people like Gov. Jennifer Granholm or Ken Salazar, the Colorado attorney general turned senator turned secretary of the interior.

Law professor at Johns Hopkins University; former law clerk to Judge Henry Friendly and Supreme Court Justice Harry Blackmun

David Souter has set the right example. By stepping down at a lively age, he has reminded the country that the Supreme Court is an institution meant to reflect the democracy it serves, as well as the timeless values of the Constitution, the common law tradition and the grounding of American law in a community of nations.

President Obama should cast a wide net to find a successor who shares Souter's broadly human qualities. The courthouse behind the Capitol is not a place for prima donnas or intellectual egos that have to prove their brilliance. Nor is it meant to be an academic hothouse. Some of the greatest justices have come from politics and law practice, alongside the appellate courts -- bringing with them knowledge of the arts of compromise and collegiality, the legitimacy of gradualism, and the processes of complex institutions. Obama should consult broadly with both sides of the aisle before settling on his choice.

This may also be a good time to reflect on the court's working methods. The aging of the bench coincides with the proliferation of law clerks, whose draft opinions are likely to mimic law review articles rather than speak to a broader public. The court's mechanical time limits on oral arguments by counsel may not serve it well, especially in areas where the court has little background (such as the law of armed conflict). In the 19th century, much longer conversations with learned counsel were permitted on matters of vast public import. And finally, the court may wish to rethink the role of friend-of-the-court briefs. These third-party filings can turn into popularity contests rather than advancing the court's understanding of applicable law and policy. They are, however, good business for lawyers.

Author of "The Selling of Supreme Court Nominees"; head of the political science department at the University of Georgia

Prior judicial experience is an overrated virtue for a Supreme Court justice. Franklin Roosevelt knew that, and Barack Obama should follow his example in naming a replacement for David Souter. FDR had nine opportunities to nominate a justice. Only two -- Harlan Fiske Stone, an associate justice whom Roosevelt elevated to chief justice, and Wiley Rutledge, a Court of Appeals judge -- were sitting judges at the time of their nomination. None of FDR's seven other nominees had previously served as a federal judge. (In fact, Stone himself hadn't when Calvin Coolidge first nominated him to be an associate justice.) And among those seven were two of the greatest justices of all time: Hugo Black and Felix Frankfurter. Throughout our history, Supreme Court justices have served with no prior experience as a judge, including John Marshall, Louis Brandeis, Robert Jackson, Earl Warren, Byron White, William Rehnquist and Lewis Powell. That's not bad company. Since 1972, every justice except Sandra Day O'Connor previously served as a federal appeals court judge.

There is no indication that this litmus test gave us better justices. Obama's nomination of someone like Elena Kagan would understandably make FDR smile.

Chairman of the Democratic Leadership Council; former House member from Tennessee

Barack Obama explained the rationale behind his Senate vote on Samuel Alito's confirmation simply -- that throughout his legal career, Alito had always sided with large and well-funded interests over the little guy. Thus, Obama voted no.

The president, a onetime editor of the Harvard Law Review and a former constitutional law professor, has spelled out over the years the kind of thinker he wants on the court: someone who interprets the Constitution as "a road map by which we marry passion to reason, the ideal of individual freedom to the demands of the community," he wrote in "The Audacity of Hope."

As he selects from a wealth of candidates, interviewing people, measuring their experience and intellect, and asking tough questions, I don't imagine a traditional litmus test will apply. No strict questions about abortion, affirmative action or torture. I hope there's a new litmus test: The court needs a broad thinker -- someone who will listen closely to the facts of cases, promote an even application of the law and not hesitate to engage fellow justices about the effect their decisions will have for future generations.

The president should be also mindful that Sasha and Malia could use another role model on the high court.

Author and professor of Law at Harvard Law School; executive director of the Charles Hamilton Houston Institute for Race & Justice; senior advisor to Barack Obama during his presidential campaign

One judicial appointment is not likely to alter the conservative trend apparent in the Supreme Court. But this first selection will offer some critical assessment of how President Obama plans to reinforce his campaign view that backbone, character, intelligence and insight concerning the life and conditions of all people are basic to quality public service. These same qualities will assist his appointee in making appropriate decisions and will reinforce the imperatives outlined in our Constitution and Bill of Rights.

The president should be willing to listen to all suggestions concerning potential nominees to the Supreme Court but be prepared, ultimately, to make a decision that reflects his philosophy about what makes a great judge. I think the president's life experiences -- including as a constitutional law teacher, community organizer and public servant -- and core values will enhance his ability to pick both a brilliant justice and someone who will be an exemplary judicial servant.

The Supreme Court needs someone with a demonstrated commitment to individual rights and a clear understanding of the court's vital role as a check on executive power. President Obama should find that person and fight for her. This is no time to choose a stealth candidate with a scant record and hope for the best. We need more than hope.

When the Democrats attain a filibuster-proof Senate majority, Obama will have the rare freedom to choose a nominee who reflects his values and vision for the country. His choice should also demonstrate what Thomas Jefferson called a "decent respect for the opinions of mankind." Interest in how others have tackled the problems we face does not corrupt our sovereignty nor undermine our democracy. As our Founding Fathers understood, it strengthens us. That respect should also encompass the views of her fellow justices, for respect is the foundation of persuasion.

Law is an increasingly technical field, but judging is, fundamentally, not the domain of experts. Most of all, it requires sound judgment. The president would do well to look for a person who has a level of engagement and experience with the world that will make the law work justice in the lives of all people who seek it.